A self-expanding stent is typically introduced into the body using a delivery device that includes an outer sheath coaxially disposed and slidable over an inner catheter to hold the stent in a low profile configuration for delivery to a treatment site. The stent is disposed at the distal end of the device between the inner catheter and the outer sheath and held in a compressed position by the outer sheath. The stent is held in the compressed position and guided through a bodily lumen to the treatment site. Once the delivery system and the stent are adjacent to the treatment site, the stent may be deployed by proximally pulling back the outer sheath relative to the inner catheter until the stent is exposed. The self-expanding stent expands from the stent distal end to the stent proximal end as the sheath is proximally withdrawn. The delivery system may include a step or other feature is provided on the inner catheter to prevent the stent from moving rearward with the outer sheath when the outer sheath is withdrawn. Some delivery devices for self-expanding stents include a trigger wire to hold the stent in position while the outer sheath is withdrawn.
As the stent is released from the outer sheath, the stent springs radially outward to an expanded diameter until the stent contacts and presses against the vessel wall. When a trigger wire is present, the trigger wire is released and the stent expands outwardly at the treatment site. Distally withdrawing the outer sheath may cause difficulty in accurately placing the proximal portion of the stent because the distal end of the stent is positioned first while the proximal portion of the stent is still covered by the outer sheath. Releasing the trigger wire from the stent at the ends allows the stent to expand and completely releases the stent from the delivery system. However, if the trigger wires are released and the stent expands into an improper position, the stent cannot be repositioned.
Similar delivery devices may also be used for delivering one or more stents to a bifurcation in a vessel. The stent may be positioned in one or more branches of the bifurcation to treat a lesion at the bifurcation. Delivery of a bifurcated stent to the treatment site in the desired position may be difficult. For example, expansion of a bifurcated stent requires non-uniform expansion forces in the main body and the branches of the stent. Release of a bifurcated stent from the delivery system by withdrawal of the outer sheath can result in improper placement of the bifurcated stent due to the non-uniform expansion of the stent when the stent is released. Similarly, release of the bifurcated stent from the trigger wires can result in improper positioning of a portion of the stent within the bifurcation.
Accordingly, in view of the drawbacks of current technology, there is a desire for a delivery system that can increase the control, accuracy and ease of placement of a bifurcated stent during deployment of the bifurcated stent within a patient. The delivery system would ideally reduce the risk of malfunction while providing for a smoother, more accurate and quicker deployment of the entire stent. The delivery system also would provide the ability to reconstrain, recapture, reposition and/or remove the bifurcated stent after expansion of the stent.